(1) Field of the Invention
The present invention relates to an oil pan for an internal combustion engine and, more particularly, to an oil pan which can regulate the movement of oil level satisfactorily.
(2) Related Art
In an internal combustion engine, lubricating oil is circulated to achieve lubrication of sliding engine parts and cooling of hot engine parts. The lubricating oil is collected in an oil pan. As shown in FIGS. 17 and 18, an internal combustion engine 102 has a cylinder head 106 mounted above a cylinder block 104 and an oil pan 108 installed below the cylinder block 104. The lubricating oil in the oil pan 108 is sucked by an oil pump 112 via a strainer 110, and supplied to a main oil gallery 116 which is a main lubricating oil passage via an oil filter 114.
The lubricating oil in the main oil gallery 116 is used to lubricate and cool a crankshaft 118 carried by the cylinder block 104, a camshaft 120 carried by the cylinder head 106, and the like. The lubricating oil which has been used for lubrication and cooling is returned to the oil pan 108.
In the oil pan 108 of this internal combustion engine 102, a baffle plate 124 is installed above the oil level 122. The baffle plate 124 is intended to regulate the movement of the oil level 122, so that the stable supply of lubricating oil is ensured and the mixing of air into the lubricating oil is prevented.
The oil pan for an internal combustion engine of this type has been disclosed in Japanese Utility Model Provisional Publication No. 2-126010 and Japanese Utility Model Provisional Publication No. 5-7917.
The oil pan disclosed in Japanese Utility Model Provisional Publication No. 2-126010 comprises an oil suction portion provided below the oil pan, a plate-shaped oil level holding portion provided substantially horizontally above the oil level of lubricating oil, and an oil level variation preventive portion provided below the oil level of lubricating oil substantially in parallel with the oil level holding portion.
The oil pan disclosed in Japanese Utility Model Provisional Publication No. 5-7917 is so designed that a baffle plate is installed to separate the oil pan side from the crankcase side, and a lubricating oil guide mechanism is installed to the baffle plate to regulate the flow of lubricating oil returning from the crankcase to the oil pan.
For the conventional oil pan 108 shown in FIGS. 17 and 18, one baffle plate 124 regulates the movement of the oil level 122. For this reason, the oil level 122 is moved easily by the movement of a vehicle, so that the amount of lubricating oil scattered by the crankshaft may increase, or the amount of air mixed in the lubricating oil may increase.
The aforementioned oil pan disclosed in Japanese Utility Model Provisional Publication No. 5-7917, which has one baffle plate, presents a similar phenomenon. The aforementioned oil pan disclosed in Japanese Utility Model Provisional Publication No. 2-126010 has two substantially horizontal baffle plates. However, the air in the oil pan cannot move rapidly, and this causes air to accumulate. This oil pan design also results in poor fluidity during casting, so that casting is more difficult.